On Wednesday, Peter read ⁵₈ of a guide book. On Thursday, he read 22 pages of the guide book. On Friday, he read ³₈ of the remaining book leaving 80 pages unread.

1. Find the number of pages read on Friday.
2. Find the total number of pages in the guide book.

(a)
Number of remaining unread pages after reading on Thursday = 8 u

Number of remaining unread pages after reading on Friday
= 8 u - 3 u
= 5 u

5 u = 80

1 u = 80 ÷ 5 = 16

Number of pages that Peter read on Friday
= 3 u
= 3 x 16
= 48

(b) 
Working backwards.

Number of pages unread after reading on Thursday
= 8 u
= 8 x 16
= 128

Total number of pages in the guide book = 8 p

Number of pages unread after reading on Wednesday 
= 8 p - 5 p
= 3 p

3 p = 22 + 128
3 p = 150

1 p = 150 ÷ 3 = 50

Total number of pages in the guide book
= 8 p
= 8 x 50
= 400

Answer(s): (a) 48; (b) 400